Dr. Barb Mattson is a good friend of mine (You should see her awesome Daisy the Model A page on Facebook) but generally is too busy to help me with these kind of things. I know she's a world-class X-Ray Astronomer though! My thought though is how dangerous could a "dark menace" be. I know a 26-lightyear radius around the Solar System is a very spartan field (about 100 known stars). All that being within Parallax range, even a faint Type 1A would be hard to miss. My reason for asking isn't to assure but to provide a worse-case scenario for a paper I'm contributing to encouraging the development on interstellar travel in the next century. It's a tenuous argument to be sure but more likely than a black hole coming out of nowhere even though we'd barely see that coming and even that that's be aiming for the sun, not for us which is still pretty bad. Hmm. You've given me a lot to think about.

I don't know where you're getting your information from but, you're somewhat wrong because if a gamma ray burst occurred 100 light years away from the earth you can kiss yourself and everybody you know goodbye because we would all be dead.

I was curious about gamma ray burst in general, and supernova is one possibility, hypernova too but the closest hypernova candidate is IIRC 3 thousand light years from Earth and no-one believes this will cause a problem either. I would again like to consider the worst case scenario though and also I choose gamma ray burst as defuse enough to make the entire solar system uninhabitable as we know it. So no escaping to Mars or Titan, per se. It's to argue that not just interplanetary but interstellar travel is a human imperative because there are some thing bigger and more dangerous than even a Chicxulub. At least, that's the theory. A simple answer would be a rotating black hole that just happens to be knocked in our direction but it would have to be feeding and again we'd see that so I don't think that can sneak up on us any more than a supernova could, even a type 1A Supernova. I'm at a loss to figure out what could "sneak up and zap up" such that it could have been sneaking up on us for millions of years unspotted until zap.

I hope we can use space.com, I think I found what ur looking for on it.http://www.space.com/5081-real-death-star-strike-earth.html
Talks about a pair of stars one named Wolf-Rayet in the constellation Sagittarius.
Wolf-Rayet is theorized to be in the last known stable phase before supernova and has a chance of producing a gamma ray.
This pin-wheel of two stars is about 8,000 light years away.